01 - Combine grapes, water, sugar, and lime juice in a blender. Blend on high speed until completely smooth and frothy, approximately 30-45 seconds.
02 - Pour the blended mixture through a fine mesh sieve or cheesecloth into a pitcher, pressing with a spoon to extract all liquid. Discard the remaining solids.
03 - Taste the agua fresca and add additional sugar or lime juice as needed to achieve desired sweetness and balance.
04 - Refrigerate until thoroughly chilled, or serve immediately over ice. Garnish glasses with fresh mint sprigs or additional grapes if desired.